Probably a joke.

First of all, we should know the measuring range (measuring range) and dividing value (minimum scale value) of the selected instrument.

For example, the measuring range of millimeter scale is 0~20cm, and the dividing value is1mm.

Readings include measured values and estimated values. For example, the millimeter scale (dividing value 1mm) reads 2. 13cm, where 2. 1cm is the measured value and 0.03cm is the estimated value.

Which number to read depends on two factors: the accuracy of the measuring instrument (that is, the minimum division value) and the experimental error.

According to the minimum scale of the instrument, the reading evaluation methods of 1/2, 1/5 and110 can be adopted respectively. Generally speaking:

The minimum division is 2 (including 0.2, 0.02, etc. ), and estimated by 1/2, such as ammeter 0 ~ 0.6A;

The minimum division is 5 (including 0.5, 0.05, etc. ), and it is estimated by 1/5, such as voltmeter 0 ~15v;

The minimum scale is 1 (including 0. 1, 0.0 1, etc. ), and it is estimated by110, such as scale, screw micrometer, ammeter 0 ~ 3A, voltmeter 0 ~ 3V, etc. When the measurement accuracy is not high or the instrument accuracy is not high enough,

Measuring instruments used in junior high school that do not need to be evaluated: vernier caliper, stopwatch, resistance box, measuring cylinder, thermometer and tray balance do not need to be evaluated when reading.